Breaking devices, such as rock drilling machines and breaking hammers, include an impact device, which is intended to provide impact pulses to a tool for breaking material being operated. The impact device has a percussion piston, which is a reciprocating object allowed to move towards an impact direction and in a return direction.
The breaking device has a pressure chamber into which the percussion piston is inserted, the percussion piston dividing the pressure chamber into a rear pressure chamber and a front pressure chamber. For moving the percussion piston into the impact direction, a high pressure is provided into the rear pressure chamber. For moving the percussion piston back, i.e. towards the return direction, a low pressure is provided in the rear pressure chamber, whereby the percussion piston moves back by an effect of a high pressure remaining constantly in the front pressure chamber.
Due to a continuous variation of the pressure of a pressure medium in the rear pressure chamber, cavitation may occur in the rear pressure chamber. The cavitation may, in turn, cause harmful deterioration of the frame of the breaking device or parts of the impact device by causing small pieces of metal to come off from the frame of the breaking device or from the parts of the impact device. This may eventually lead to a leakage of pressure medium via a hole appearing through the wall of the frame of the breaking device or malfunctions of the breaking device because of loose pieces entering between moving parts in the impact device.